1. Field of the Invention
The present invention relates to an optical head for writing data to and reading data from a magneto-optical disk.
2. Description of the Related Art
A conventional optical head of this kind is disclosed, for example, in JP-A-02(1990)-18720. For clarity, reference is now made to FIGS. 19 and 20 of the present application to describe the optical head disclosed in this publication.
As shown in FIG. 19, the prior art optical head includes a mirror M and a slider S. The mirror M is directly supported on a tip end of a main arm A, whereas the slider S is indirectly supported on the tip end of the main arm A via a suspension arm Sa. The main arm A is movable back and forth radially of a magneto-optical disk D which rotates at a high speed on a spindle (not shown). The slider S carries an object lens L and a coil block Cb. The coil block Cb has a considerable thickness and is formed with a tapered hole TH concentric with an optical axis of the object lens L. The underside of the coil block Cb is provided with a coil C surrounding the tapered hole TH.
The optical head having such a structure is referred to as a front-illumination-type head because it directly faces the recording layer of the magneto-optical disk D. In operation, when a laser beam advancing horizontally is reflected by the mirror M for entering the object lens L which then causes the laser beam to converge, thereby forming a laser spot Ls on the recording layer of the disk D. The coil C generates an external magnetic field needed for writing data from and reading data onto the recording layer of the disk D at the laser spot Ls. In this optical head, since the slider S itself is provided with the coil C, there is no need to separately provide a magnetic head for generation of an external magnetic field, so that it is possible to reduce the apparatus size. Further, since the coil C is positioned the disk D, it is capable of efficiently generating an external magnetic field for application to the recording layer of the disk.
However, the prior art optical head still has problems to be solved, as described below.
Referring to FIG. 20, the laser beam proceeds at an angle i within the object lens L but goes out from the lower lens surface 90 into an air space at a larger angle r before reaching the magneto-optical disk D. This is because air has the smallest refractive index among various media including a glass material of which the object lens L is made. The angle xcex1 of incidence of the laser beam onto the disk D (the converging angle being 2xcex1) is equal to the outgoing angle r.
According to the prior art described above, the tapered hole TH of the coil block Cb is an unoccupied space. Therefore, even if the coil C is positioned close to the magneto-optical disk D to the extent of virtually contacting it, the thickness or height S2 of the air layer between the lens surface 90 and the disk D is no less than the combined thickness of the coil block Cb and the coil C. As a result, the laser beam path from the lens surface 90 to the disk D becomes inevitably long.
On the other hand, an attempt is made in recent years to increase the NA (numerical aperture) of an object lens for realizing a higher-density recording of data onto a magneto-optical disk. For realizing an NA increase in the above-described optical head (namely for increasing the outgoing angle r in FIG. 20), it is necessary to diametrically increasing the coil block Cb and the tapered hole TH or to reduce the combined thickness of the coil block Cb and the coil, in addition to diametrically increasing the object lens L itself. However, the size increase of the object lens L and the coil block Cb is impractical because it will result in a weight increase which hinders high-speed access by the optical head, besides difficulty of efficiently generating a magnetic field at the laser spot Ls. Further, a decrease of the thickness of the coil block Cb leads to difficulty in the realization of machining and assembling precision. Moreover, since the travel path of the laser beam in the air gap after exiting from the object lens is long, it is difficult to perform focusing adjustment due to the need for strictly defining this long path. Conventionally, all these have been factors that have hindered high-density recording of data onto the magneto-optical disk.
It is, therefore, an object of the present invention to provide an optical head which is capable of reducing machining and/or assembling difficulties for facilitating laser beam focusing while realizing an NA increase of the object lens with effective generation of a magnetic field.
According to a first aspect of the present invention, an optical head comprises a lens carrier movable at least radially of a magneto-optical disk in facing relation thereto. An object lens is mounted on the lens carrier to converge a laser beam for forming a laser spot on the disk. The object lens has an optical axis and includes a lens surface directed toward the disk. A patterned coil is formed on the lens surface at least in one layer. The coil has a light-passing opening corresponding to the optical axis of the object lens. A light-pervious layer is formed on the lens surface for closing the light-passing opening of the coil.
Preferably, the light-pervious layer may be equal or substantially equal in refractive index to the object lens.
Preferably, the light-pervious layer may entirely cover the coil.
In one embodiment of the first aspect of the present invention, the object lens has an opposite pair of side surfaces each of which is provided with an electrode in electrical connection to the coil. The electrode may have an end surface flush with the lens surface, and the coil may extend onto the end surface of the electrode in electrical contact therewith. Alternatively, the electrode may be in the form of a conductor film extending from a respective one of the side surfaces of the object lens to the lens surface into electrical contact with the coil.
In another embodiment of the first aspect of the present invention, the object lens has a side surface which is provided with a pair of electrodes in electrical connection to the coil.
In a further embodiment of the first aspect of the present invention, the lens carrier has a surface flush with the lens surface, and the light-pervious layer extends onto said surface of the lens carrier. In this case, the lens carrier may be provided with a pair of electrodes each extending onto said surface of the lens carrier for electrical contact with the coil.
Preferably, the optical head may further comprises an additional object lens mounted on the lens carrier at a side away from the disk.
Preferably, the lens carrier may be in the form of a slider elastically supported to float slightly from the disk in rotation.
According to a second aspect of the present invention, there is provided an optical head comprising a lens carrier movable at least radially of a magneto-optical disk in facing relation thereto. An object lens is mounted on the lens carrier to converge a laser beam for forming a laser spot on the disk. The object lens has an optical axis and includes a lens surface directed toward the disk. A light-pervious substrate includes a first surface bonded to the lens surface, and a second surface directed toward the disk. A patterned coil is formed on the second surface of the substrate at least in one layer. The coil has a light-passing opening corresponding to the optical axis of the object lens. A light-pervious layer is formed on the second surface of the substrate for closing the light-passing opening of the coil.
Preferably, the substrate and the light-pervious layer may be equal or substantially equal in refractive index to the object lens.
Preferably, the light-pervious layer may entirely cover the coil.
In one embodiment of the second aspect of the present invention, the substrate is provided with a pair of electrodes in electrical connection to the coil. Preferably, each of the electrodes may have an end surface flush with the second surface of the substrate, and the coil may extend onto the end surface of the electrode in electrical contact therewith. Further, each of the electrodes may penetrate through the substrate. Alternatively, each of the electrodes may comprise a conductor film extending from a side edge of the substrate to the second surface thereof into electrical contact with the coil.
Preferably, the optical head may further comprise an additional object lens mounted on the lens carrier at a side away from the disk.
Preferably, the lens carrier may be in the form of a slider elastically supported to float slightly from the disk in rotation.
According to a third aspect of the present invention, there is provided an optical head comprising a lens carrier movable at least radially of a magneto-optical disk in facing relation thereto. The lens carrier includes a support wall having a surface directed toward the disk. The support wall is formed with a light-passing hole. An object lens is mounted on the support wall of the lens carrier inside thereof to converge a laser beam for forming a laser spot on the disk. The object lens has an optical axis in alignment with the light-passing hole of the support wall. A patterned coil is formed on said surface of the support wall at least in one layer. The coil has a light-passing opening corresponding to the optical axis of the object lens. A light-pervious layer is formed on said surface of the support wall for closing the light-passing hole of the support wall and the light-passing opening of the coil.
Preferably, the light-pervious layer may be equal or substantially equal in refractive index to the object lens.
Preferably, the light-pervious layer may entirely cover the coil.
In one embodiment of the third aspect of the present invention, the lens carrier is provided with a pair of electrodes in electrical connection to the coil. Preferably, each of electrodes may penetrate through the lens carrier.
Preferably, the optical head may further comprise an additional object lens mounted on the lens carrier at a side away from the disk.
Preferably, the lens carrier may be in the form of a slider elastically supported to float slightly from the disk in rotation.
These and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the present invention given with the accompanying drawings.